Indexable microscopes, which comprise several optical components that can be switched into and out of the beam path, are known from a variety of microscopy application sectors. U.S. Pat. No. 5,633,752, for example, describes an incident-light fluorescence microscope having a special indexing apparatus for the fluorescence device. This microscope encompasses a disk-shaped base which is secured in the microscope housing and on which three rotary disks, mounted in coaxially rotatable fashion, are arranged one above another. Several absorption filters are arranged in different index positions on the first rotary disk, a corresponding number of excitation filters are arranged on the second rotary disk, and dichroic mirrors corresponding to the index positions are arranged on the third rotary disk. A respectively switched-in combination of absorption filter, excitation filter, and dichroic mirror constitutes a fluorescence device, which are usually combined into a fluorescence block. The resulting total height for the overall assemblage together with the baseplate is made up of the height of a usual fluorescence block plus, in addition, the thickness of the two rotary disks arranged thereabove. Because the baseplate at the same time is in contact at the bottom against the housing, the indexing apparatus cannot be supplemented with further elements.
German Unexamined Application DE 101 19 909 A1 also describes an indexable microscope having multiple indexable assemblies. Arranged on this are optical components that can be selectably inserted into the beam path. Various beam splitters or various tube lenses, for example, are arranged, as selectably insertable optical components, on the indexable assemblies. Because of the physical arrangement of the mechanical assemblies that are to be indexed separately, a considerable volume must be provided for installation of those assemblies in the microscope stand.